According to an analysis of the genetics of a pike population in southern Europe, researchers have proposed the existence of an entirely separate species of fish: the southern pike, or Esox flaviae.
Lead author of the study, Livia Lucentini and eight co-authors examined pike from continental Europe, and southern and central Italy, comparing morphology, population genetics and DNA taxonomy between the common northern pike (Esox lucius) and the suspected different species.
The main reason behind the study was to ensure that genetics were not crossed in attempting to restock a declining northern pike population in Mediterranean countries with what were assumed to be northern pike from the regions of the study. More simply put – the study was meant to ensure there would be no hybridization between species.
What Lucentini and her team discovered were distinct genetic, taxonomic and morphologic differences between the common northern pike, and the proposed species in question. The strongest differences include dissimilar color and skin pattern, and a consistently different number of scales along the lateral line for each species.
The skin of the northern pike is decorated by round spots and while the body of the fish may vary in color based on habitat or geography, the round spot pattern remains consistent in the species. However, the southern pike is wildly different in appearance. It exhibits four very different skin patterns depending on habitat and geographical location, including diagonal bars, vertical bars, longitudinal bars and what is called a stellate spot pattern. The pattern that is never found in this species however, is the round spot pattern of the northern pike.
The second key differentiator in the southern pike is the number of scales found along the lateral line. While the northern pike will have between 101 and 115 scales along the lateral line, the southern pike always exhibits significantly more. All sampled Esox flaviae tallied no less than 125 scales and no more than 148 scales along the lateral line.
The conclusion of the study not only insists on a ban on the introduction of these pike into regions of dwindling northern pike for the purpose of preventing hybridization, it proposes an entirely new species of fish: the southern pike.